In my opinion 2005 Yiwu Mansa is slightly better than 2003 Yiwu Zhengshan from the same factory (Manluo). And 2003 Yiwu Ancient Trees is better than both of them, having very similar taste profile. I recommend you to try their own production. Even their cheapest shengs are bright and powerful. I have tried and enjoyed 0901 (clone of 7542 that Hobbes once called Project Manhattan), 1207 (clean and cooling), 1205 (tons of energy), 1206 (pleasantly soapy Lincang).

This depends what you are comfortable drinking. The 2007 and 2008 Xia Guan you mentioned (panchen/baoyan) are going to be really, really rough at this age, especially if they were stored in a dry environment.